The present invention relates, in general, to document identification. More specifically, the present invention relates to an apparatus and method for discriminating among a plurality of document types such as currency bills of different denominations and/or from different countries.
Machines that are currently available for simultaneous scanning and counting of documents such as paper currency are relatively complex and costly, and relatively large in size. The complexity of such machines can also lead to excessive service and maintenance requirements. These drawbacks have inhibited more widespread use of such machines, particularly in banks and other financial institutions where space is limited in areas where the machines are most needed, such as teller areas. The above drawbacks are particularly difficult to overcome in machines which offer much-needed features such as the ability to scan bills regardless of their orientation relative to the machine or to each other, and the ability to authenticate genuineness and/or denomination of the bills.
A variety of techniques and apparatus have been used to satisfy the requirements of automated currency handling systems. At the lower end of sophistication in this area of technology are systems capable of handling only a specific type of currency, such as a specific dollar denomination, while rejecting all other currency types. At the upper end are complex systems which are capable of identifying and discriminating among and automatically counting multiple currency denominations.
Currency discrimination systems typically employ either magnetic sensing or optical sensing for discriminating among different currency denominations. Magnetic sensing is based on detecting the presence or absence of magnetic ink in portions of the printed indicia on the currency by using magnetic sensors, usually ferrite core-based sensors, and using the detected magnetic signals, after undergoing analog or digital processing, as the basis for currency discrimination. A variety of currency characteristics can be measured using magnetic sensing. These include detection of patterns of changes in magnetic flux, patterns of vertical grid lines in the portrait area of bills, the presence of a security thread, total amount of magnetizable material of a bill, patterns from sensing the strength of magnetic fields along a bill, and other patterns and counts from scanning different portions of the bill such as the area in which the denomination is written out.
The more commonly used optical sensing techniques, on the other hand, are based on detecting and analyzing variations in light reflectance or transmissivity characteristics occurring when a currency bill is illuminated and scanned by a strip of focused light. The subsequent currency discrimination is based on the comparison of sensed optical characteristics with prestored parameters for different currency denominations, while accounting for adequate tolerances reflecting differences among individual bills of a given denomination. A variety of currency characteristics can be measured using optical sensing. These include detection of a bill""s density, color, length and thickness, the presence of a security thread and holes, and other patterns of reflectance and transmission. Color detection techniques may employ color filters, colored lamps, and/or dichroic beamsplitters.
In addition to magnetic and optical sensing, other techniques of detecting characteristic information of currency include electrical conductivity sensing, capacitive sensing (such as for watermarks, security threads, thickness, and various dielectric properties) and mechanical sensing (such as for size, limpness, and thickness).
A major obstacle in implementing automated currency discrimination systems is obtaining an optimum compromise between the criteria used to adequately define the characteristic pattern for a particular currency denomination, the time required to analyze test data and compare it to predefined parameters in order to identify the currency bill under scrutiny, and the rate at which successive currency bills may be mechanically fed through and scanned. Even with the use of microprocessors for processing the test data resulting from the scanning of a bill, a finite amount of time is required for acquiring samples and for the process of comparing the test data to stored parameters to identify the denomination of the bill.
Recent currency discriminating systems rely on comparisons between a scanned pattern obtained from a subject bill and sets of stored master patterns for the various denominations among which the system is designed to discriminate. For example, it has been found that scanning U.S. bills of different denominations along a central portion thereof provides scanning patterns sufficiently divergent to enable accurate discrimination between different denominations. Such a discrimination device is disclosed in U.S. Pat. No. 5,295,196. However, currencies of other countries can differ from U.S. currency and from each other in a number of ways. For example, while all denominations of U.S. currencies are the same size, in many other countries currencies vary in size by denomination. Furthermore, there is a wide variety of bill sizes among different countries. In addition to size, the color of currency can vary by country and by denomination. Likewise, many other characteristics may vary between bills from different countries and of different denominations.
As a result of the wide variety of currencies used throughout the world, a discrimination system designed to handle bills of one country generally can not handle bills from another country. Likewise, the method of discriminating bills of different denominations of one country may not be appropriate for use in discriminating bills of different denominations of another country. For example, scanning for a given characteristic pattern along a certain portion of bills of one country, such as optical reflectance about the central portion of U.S. bills, may not provide optimal discrimination properties for bills of another country, such as German marks.
Furthermore, there is a distinct need for an identification system which is capable of accepting bills of a number of currency systems, that is, a system capable of accepting a number of bill-types. For example, a bank in Europe may need to process on a regular basis French, British, German, Dutch, etc. currency, each having a number of different denomination values.
Furthermore, in currency discriminating systems that rely on comparisons between a scanned pattern obtained from a subject bill and sets of stored master patterns, the ability of a system to accurately line up the scanned patterns to the master patterns to which they are being compared is important to the ability of a discrimination system to discriminate among bills of various denominations as well as between genuine bills and counterfeit bills without rejecting an unacceptable number of genuine bills. However, the ability of a system to line up scanned and master patterns is often hampered by the improper initiation of the scanning process which results in the generation of scanned patterns. If the generation of scanned patterns is initiated too early or too late, the resulting pattern will not correlate well with the master pattern associated with the identity of the currency; and as a result, a genuine bill may be rejected. There are a number of reasons why a discrimination system may initiate the generation of a scanned pattern too early or too late, for example, stray marks on a bill, the bleeding through of printed indicia from one bill in a stack onto an adjacent bill, the misdetection of the beginning of the area of the printed indicia which is desired to be scanned, and the reliance on the detection of the edge of a bill as the trigger for the scanning process coupled with the variance, from bill to bill, of the location of printed indicia relative to the edge of a bill. Therefore, there is a need to overcome the problems associated with correlating scanned and master patterns.
It is an object of the present invention to provide an improved method and apparatus for identifying documents.
It is an object of the present invention to provide an improved method and apparatus for discriminating among currency bills comprising a plurality of currency denominations.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of efficiently discriminating among bills of several currency denominations at a high speed and with a high degree of accuracy.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of efficiently discriminating currencies from a number of different countries.
It is another object of this invention to provide a currency evaluation device able to discriminate among different denominations of bills from two or more currency systems.
It is another object of this invention to provide a currency evaluation device able to discriminate among different denominations of both Canadian and German bills.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of scanning a document such as a currency bill along two or more laterally displaced segments to thereby identify the document.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of scanning a document along two or more laterally displaced segments by using two or more laterally displaced scanheads.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of scanning a document along two or more laterally displaced segments by using two or more laterally displaced sensors of a linear array scanhead.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of scanning a document along two or more laterally displaced segments by using one or more laterally moveable scanheads.
It is another object of this invention to provide an improved method and apparatus of the above kind wherein the above scanheads or sensors retrieve optical reflectance information from a document under test and use such reflectance information to determine the identity of the document.
It is another object of this invention to provide an improved method and apparatus of the above kind which identifies a document by comparing one or more scanned patterns generated by scanning a document under test with one or more scanheads or one or more sensors and comparing the scanned pattern or patterns with one or more master patterns associated with genuine documents.
It is another object of this invention to provide an improved method and apparatus of the above kind which identifies a document by determining the size of the document.
It is another object of this invention to provide an improved method and apparatus of the above kind which identifies a document by determining the color of the document.
It is another object of this invention to provide an improved method and apparatus of the above kind which identifies a document based on a combination of size information and scanned/master pattern comparison.
It is another object of this invention to provide an improved method and apparatus of the above kind which identifies a document based on a combination of color information and scanned/master pattern comparison.
It is another object of this invention to provide an improved method and apparatus of the above kind which identifies a document based on a combination of size information, color information, and scanned/master pattern comparison.
It is another object of this invention to provide an improved method and apparatus of the above kind in which only selected ones of a number of scanheads or sensors are activated to scan a document.
It is another object of this invention to provide an improved method and apparatus of the above kind in which scanned patterns are generated only from the output or data derived therefrom of selected ones of a number of scanheads or sensors which are activated to scan a document.
It is another object of this invention to provide an improved method and apparatus of the above kind in which the selection of one or more of a number of scanheads or sensors to scan a document is based on size information.
It is another object of this invention to provide an improved method and apparatus of the above kind in which the selection of one or more of a number of scanheads or sensors to scan a document is based on color information.
It is another object of this invention to provide an improved method and apparatus of the above kind in which the lateral positioning of one or more moveable scanheads is based on size and/or color information detected from the document.
It is another object of this invention to provide an improved method and apparatus of the above kind in which the selection of the output or data derived therefrom of one or more of a number of scanheads or sensors for the generation of scanned patterns is based on size information.
It is another object of this invention to provide an improved method and apparatus of the above kind in which the selection of the output or data derived therefrom of one or more of a number of scanheads or sensors for the generation of scanned patterns is based on color information.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of scanning either side or both sides of a document.
It is another object of this invention to provide an improved method and apparatus of the above kind in which the amount of information that must be processed is reduced by tailoring the areas from which scanned patterns are derived, such reduction being based on pre-scan information detected from a document such as the size and/or color of a document to be scanned.
It is another object of this invention to provide an improved method and apparatus of the above kind in which the amount of information that must be processed is reduced by tailoring the data which must be assembled into one or more scanned patterns, such reduction being based on information detected from a document during the scanning process itself, the information detected during the scanning process itself including, for example, size and/or color information.
It is another object of this invention to provide an improved method and apparatus of the above kind in which size and/or color information detected from a document is used to generate a preliminary set of potentially matching documents and in which one or more scanned patterns generated from a document are compared with master patterns chosen from the preliminary set.
It is another object of this invention to provide an improved method and apparatus of the above kind in which a document to be scanned is transported past one or more scanheads in a centered or justified manner along a transport path.
It is another object of this invention to provide an improved method and apparatus of the above kind in which a document to be scanned is transported past one or more scanheads along a transport path and in which one or more sensors separate from the one or more scanheads are used to determine the lateral positioning of the document within the transport path.
It is another object of this invention to provide an improved method and apparatus of the above kind in which a document to be scanned is transported past one or more scanheads along a transport path and in which the lateral positioning of the document within the transport path is determined by analyzing the output of one or more scanheads.
It is another object of this invention to provide an improved method and apparatus of the above kind in which a document to be scanned is transported past one or more scanheads along a transport path and in which the skew of the document is determined by analyzing of output of one or more scanheads or analyzing the output of one or more separate sensors.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of accepting documents fed either face up or face down.
It is another object of this invention to provide an improved method and apparatus of the above kind which is capable of accepting documents fed in either the forward or reverse direction, i.e., top edge first or top edge last.
A related object of the present invention is to provide such an improved currency discrimination and counting apparatus which is compact, economical, and has uncomplicated construction and operation.
It is an object of the present invention to provide an improved currency scanning and counting machine which is relatively simple and compact, while at the same time providing a variety of advanced features which make the machine convenient and useful to the operator.
Another object of this invention is to provide such an improved currency scanning and counting machine that is relatively inexpensive to manufacture and maintain, and which also facilitates service and maintenance. In this connection, a related object of the invention is to provide such a machine having a relatively small number of parts, and in which most of the parts are arranged in a manner to have a long operating life with little or no maintenance.
It is a further object of this invention to provide such a machine that is capable of operating at a faster throughput rate than any previous machine able to determine the denomination of the scanned bills.
It is another object of the present invention to provide an improved method and apparatus for identifying a currency as belonging to a set of one or more currency bills.
It is another object of the present invention to provide an improved method and apparatus for determining the identity of a currency bill.
It is another object of the present invention to provide an improved method of generating modified scanned patterns.
It is another object of the present invention to provide an improved method of generating modified master patterns.
It is another object of the present invention to provide an improved method and apparatus for determining the identity of a currency bill by comparing a modified version of a scanned pattern with one or more master patterns.
It is another object of the present invention to provide an improved method and apparatus for determining the identity of a currency bill by comparing modified versions of one or more master patterns with a scanned pattern.
It is another object of the present invention to provide an improved method and apparatus using an improved pattern generation method for improving the ability of a discrimination system to accurately reject improper bills while reducing the likelihood of rejecting genuine bills.
Other objects and advantages of the invention will become apparent upon reading the following detailed description in conjunction with the accompanying drawings.
In accordance with an embodiment of the present invention, the foregoing objectives are realized by providing a currency counting and discrimination device for receiving a stack of currency bills, rapidly counting and discriminating the bills in the stack, and then re-stacking the bills. This device includes an input receptacle for receiving a stack of currency bills to be discriminated, a discriminating unit for discriminating the currency bills by denomination, an output receptacle for receiving the currency bills after they have been discriminated, and a transport mechanism for transporting the currency bills, one at a time, from the input receptacle past the discriminating unit and to the output receptacle. The transport mechanism includes stripping wheels for stripping the lowermost bill from a stack of bills in the input receptacle, and a pair of driven transport rolls on opposite sides of the discriminating unit for transporting each bill past the discriminating unit. One of the transport rolls also receives bills directly from the stripping wheels and transports the received bills to the region between the pair of transport rolls.
In a preferred embodiment, a pair of photosensors are located at opposite sides of the bill transport path, each photosensor including a light source and a protective lens on one side of the bill, and a photodetector and a protective lens on the other side of the bill. The lenses for both the light sources and the photodetectors are located sufficiently close to each other that the lenses are wiped by the bills transported therebetween.
In accordance with an embodiment of the present invention, the objectives enumerated above are achieved by scanning a document along one or more segments, generating one or more scanned patterns therefrom, and comparing the one or more scanned patterns to one or more master patterns associated with scans along corresponding segments of genuine documents. A preferred embodiment of the present invention involves a technique based on the optical sensing of reflectance characteristics obtained by illuminating and scanning a document such as a currency bill along an appropriately selected segment or segments of a document. Light reflected from the bill as it is optically scanned is detected and used as an analog representation of the variation in the dark and light content of the printed pattern or indicia on the bill surface.
A series of such detected reflectance signals are obtained by sampling and digitally processing, under microprocessor control, the reflected light at a plurality of predefined sample points as the bill is moved across the illuminated strip. Accordingly, a fixed number of reflectance samples is obtained across the note. The data samples obtained for a bill scan are subjected to digital processing, including a normalizing process to deaccentuate variations due to contrast fluctuations in the printed pattern or indicia existing on the surface of the bill being scanned. The normalized reflectance data represent a characteristic pattern that is fairly unique for a given bill identity and incorporates sufficient distinguishing features between characteristic patterns for different bill-types so as to accurately differentiate therebetween.
By using the above approach, a series of master characteristic patterns are generated and stored using standard bills for each denomination of currency that is to be detected. The xe2x80x9cstandardxe2x80x9d bills used to generate the master characteristic patterns are preferably bills that are slightly used bills. According to a preferred embodiment, two or four characteristic patterns are generated and stored within system memory for each detectable bill-type. The stored patterns correspond, respectively, to optical scans performed on one or both sides of a bill along xe2x80x9cforwardxe2x80x9d and xe2x80x9creversexe2x80x9d directions relative to the pattern printed on the bill. For bills which produce significant pattern changes when shifted slightly to the left or right, such as the $10 bill in U.S. currency, it is preferred to store two patterns for each of the xe2x80x9cforwardxe2x80x9d and xe2x80x9creversexe2x80x9d directions, each pair of patterns for the same direction represent two scan areas that are slightly displaced from each other along the lateral dimension of the bill. Preferably, the document identification system of this invention is adapted to identify different denominations of a plurality of currency systems. Accordingly, a master set of different characteristic patterns is stored within the system memory for subsequent correlation purposes.
According to the correlation technique of this invention, the pattern generated by scanning a bill under test and processing the sampled data is compared with each of the prestored characteristic patterns within a preliminary set (to be described below) to generate, for each comparison, a correlation number representing the extent of similarity between corresponding ones of the plurality of data samples for the compared patterns. Bill identification is based on designating the scanned bill as belonging to the bill-type corresponding to the stored characteristic pattern for which the correlation number resulting from pattern comparison is determined to be the highest. The possibility of a scanned bill having its identity mischaracterized following the comparison of characteristic patterns is significantly reduced by defining a bi-level threshold of correlation that must be satisfied for a xe2x80x9cpositivexe2x80x9d call to be made.
In essence, the present invention utilizes an optical sensing and correlation technique for positively identifying any of a plurality of different bill-types regardless of whether the bill is scanned along the xe2x80x9cforwardxe2x80x9d or xe2x80x9creversexe2x80x9d directions. Likewise in a preferred embodiment of the present invention, the system is capable of identifying any of a plurality of different bill-types regardless of whether the bill is fed into the system with a xe2x80x9cface upxe2x80x9d or xe2x80x9cface downxe2x80x9d orientation. Face orientation can be accommodated by storing master patterns scanned from both sides of genuine documents, using a system having one or more scanheads on a single side of a document transport path, and comparing scanned patterns to master patterns retrieved from both sides of genuine documents. Alternatively, scanheads may be placed on both sides of a document transport path, scanned patterns retrieved from respective sides can be compared to master patterns from both sides or master patterns from corresponding sides where face orientation can be determined. Additionally, a cross check can be performed so that the identity determined by a match of patterns from one side of a document is consistent with the identity indicated by comparing patterns from the other side of the document. For both one-sided and two-sided scanhead systems, where the face orientation of a document can be determined before patterns are compared, scanned patterns from one side of a document can be compared only to master patterns retrieved from a corresponding side. Similar methods can be employed for accommodating documents fed in forward and reverse directions.
In a preferred embodiment, the invention is particularly adapted to be implemented with a system programmed to track each identified currency identity so as to conveniently present aggregate totals for bills that have been identified at the end of a scan run. A preferred embodiment incorporates an abbreviated curved transport path for accepting currency bills that are to be counted and transporting the bills about their narrow dimension across a scanhead located downstream of the curved path and onto a conventional stacking station where sensed and counted bills are collected. In a preferred embodiment, a scanhead of the present invention operates in conjunction with an optical encoder which is adapted to initiate the capture of a predefined number of reflectance data samples when a bill (and, thus, the indicia or pattern printed thereupon) moves across a coherent strip of light focused by the scanhead.
In a preferred embodiment, a scanhead of the present invention uses a pair of light-emitting diodes (xe2x80x9cLEDsxe2x80x9d) to focus a coherent light strip of predefined dimensions and having a normalized distribution of light intensity across the illuminated area. The LEDs are angularly disposed and focus the desired strip of light onto the narrow dimension of a bill positioned flat across the scanning surface of the scanhead. A photodetector detects light reflected from the bill. The sampling of the photodetector output is controlled by the optical encoder to obtain the desired reflectance samples. Initiation of sampling is based upon detection of the edge of a bill.
The above described techniques and apparatus as tailored to scanning U.S. currency are more fully disclosed in U.S. Pat. No. 5,295,196, for a xe2x80x9cMethod and Apparatus for Currency Discrimination and Countingxe2x80x9d incorporated herein in its entirety.
In adapting the currency discriminating method and apparatus disclosed in U.S. Pat. No. 5,295,196 to optimize the scanning of currencies from countries other than the United States, it is first noted that while it has been found that scanning along the central portion of the green side of U.S. bills provides good patterns to discriminate between the different U.S. denominations, foreign bills may require scanning along segments located in locations other than the center and the desirable areas to scan bills can vary from bill-type to bill-type. For example, it may be determined that it is desirable to scan German marks in the forward direction along a segment 1 inch (2.54 cm) to the left of center along the top face of a bill while it may be desirable to scan British pounds along a segment 1.5 inches (3.81 cm) to the right of center. To provide a system capable of scanning along a plurality of laterally displaced segments, the present invention utilizes either a plurality of laterally displaced stationary scanheads, one or more laterally moveable scanheads, or a linear array scanhead having a plurality of laterally displaced sensors. In a preferred embodiment, the scanheads or sensors are arranged in a symmetrical manner about the center of document to be scanned. Such a symmetrical arrangement aids in providing a system which is capable of accepting bills fed in both the forward and reverse directions.
Additionally, while all denominations of U.S. currency have the same size, currencies from other countries may vary in size from country to country as well as from denomination to denomination for currency from the same country. In a preferred embodiment of the present invention, variance in size is accommodated by incorporating means for determining the size of a document. These size determining means may include sensors separate from the scanheads or scanning sensors discussed above or alternatively, in some preferred embodiments of the present invention, may include the scanheads or scanning sensors discussed above which are used for the retrieval of scanned characteristic patterns. Based on the size information retrieved from a bill, selected scanheads may be activated, laterally moveable scanheads may be appropriately positioned and activated, and/or selected sensors in a linear array scanhead may be activated to permit scanning along appropriate segments of a bill based on its size. Alternatively, all scanheads or scanning sensors may be activated and the output of appropriately positioned scanheads or scanning sensors may be processed to generate scanned patterns based on the size of a bill. Furthermore, based on the size of a bill, a preliminary determination can be made as to which of a plurality of genuine bill-types a bill under test may potentially match. Based on such a preliminary determination, the comparison of generated scanned patterns can be limited to only master patterns associated with bill-types chosen from the preliminary set of potentially matching bills.
Likewise, the transport mechanism which transports documents to be scanned past the above described scanheads may be designed to transport documents in a centered manner, left or right justified manner, in a non-controlled lateral positioned manner, in a non-skewed manner, or in a skewed manner. Sensors separate and distinct from the above described scanheads or the above described scanheads themselves may be used to determine the lateral positioning of transported bills and/or their degree of skew. Based on a determination of the laterally positioning of a bill and/or its skew, appropriately positioned scanheads or scanning sensors may be activated or laterally moveable scanheads may be appropriately positioned and activated or the output from appropriately positioned scanheads or scanning sensors may be processed to generate scanned patterns based on the lateral positioning and/or skew of the bill.
Additionally, while all denominations of U.S. currency have the same colors (a xe2x80x9cgreenxe2x80x9d side and a xe2x80x9cblackxe2x80x9d side), currencies from other countries may vary in color from country to country as well as from denomination to denomination for currency from the same country. In a preferred embodiment of the present invention, variance in color is accommodated by incorporating means for determining the color of a document. These color determining means may include sensors separate from the scanheads or sensors discussed above or alternatively, in some preferred embodiments of the present invention, may include the appropriately modified scanheads or sensors discussed above which are used for the retrieval of scanned characteristic patterns. For example, colored filters may be placed in front of the above described scanheads or sensors. Based on the color information retrieved from a bill, selected scanheads may be activated, laterally moveable scanheads may be appropriately positioned and activated, and/or selected sensors in a linear array scanhead may be activated to permit scanning along appropriate segments of a bill based on its color. Alternatively, all scanheads or scanning sensors may be activated and the output of appropriately positioned scanheads or scanning sensors may be processed to generate scanned patterns based on the color of a bill. Furthermore, based on the color of a bill, a preliminary determination can be made as to which of a plurality of genuine bill-types a bill under test may potentially match. Based on such a preliminary determination, the comparison of generated scanned patterns can be limited to only master patterns associated with bill-types chosen from the preliminary set of potentially matching bills.
In a preferred embodiment of the present invention, both color and size information may be utilized as described above.
In a preferred embodiment of the present invention, scanheads are positioned on both sides of a document transport path so as to permit scanning of either or both sides of a document.
Furthermore, in accordance with another feature of the present invention, the objectives enumerated above in connection with correlating patterns are achieved by repetitively comparing a scanned pattern with multiple sets of master patterns until a sufficient match is found, or alternatively, by repetitively comparing a set of original master patterns with multiple scanned patterns until a sufficient match is found. The multiple sets of master patterns comprise an original set of master patterns plus one or more sets of modified versions of the original master patterns. The multiple scanned patterns comprise an original scanned pattern plus one or more modified versions of the original scanned patterns. Each modified pattern comprises one or more replicated data values from a corresponding original pattern to which each modified pattern is to be compared. Alternatively, each modified master pattern comprises one or more data values which are set equal to zero.
Briefly, in accordance with a preferred embodiment, an improved method of generating modified scanned or master patterns for use in a discrimination system capable of identifying one or more currency bills is provided. Each of the scanned and master patterns comprises a sequence of data values representing analog variations of characteristic information along a segment of a bill and each pattern has a leading end and a trailing end. Each of the data values has an associated sequence position. The modified scanned or master patterns are generated by designating either the scanned pattern or the master pattern for modification and inserting a predetermined number, R, of data values at either the trailing end of the sequence of data values of the designated pattern when the modification is performed in the forward direction or the leading end of the sequence of data values of the designated pattern when the modification is performed in the backward direction. This modification effectively removes R data values from the leading or trailing end of the designated pattern. Either the last R data values of the designated pattern are set equal to the last R data values of the non-designated pattern when the modification is performed in the forward direction or the first R data values of the designated pattern are set equal to the first R data values of the non-designated pattern when the modification is performed in the backward direction. Alternatively, the modified master patterns are generated by inserting R data samples at the leading or trailing ends of the master patterns and by setting the first R or last R data samples of the modified master pattern equal to zero.
According to a preferred method, a modified scanned pattern is generated by removing a predetermined number of leading or trailing data values of an original scanned pattern. Trailing or leading data values, respectively, are added to the modified scanned pattern with the added data values being copied from corresponding sequence positions of a corresponding master pattern. Alternatively, instead of explicitly removing leading or trailing data values, the leading or trailing data values may be effectively removed by adding data values to the opposite end of the scanned pattern and treating the modified scanned pattern as not including the xe2x80x9cremovedxe2x80x9d leading or trailing data values.
According to another preferred method, a modified master pattern is generated in a similar manner except that added trailing or leading data values of the modified master pattern are set equal to data values copied from corresponding sequence positions of a scanned pattern.
According to another preferred method, a modified master pattern is generated in a similar manner except that added trailing or leading data values of the modified master pattern are set equal to zero.
The above described modified patterns or pattern generation methods may be employed in currency identification systems to compensate for misalignment between scanned and master patterns.
According to another preferred method, a scanned pattern comprising a number of data values is compared with one or more master patterns also comprising a number of data values. The scanned and master patterns represent analog variations in characteristic information retrieved from bills along corresponding segments. For example, the patterns may comprise 64 data values generated by sampling the output of a photodetector as a bill is moved relative to a scanhead, the output of the photodetector representing analog variation in the reflectance of light along a given segment of the bill. If none of the master patterns sufficiently match the scanned pattern, the scanned pattern may be modified and the modified scanned pattern compared to the master patterns. For example, data values #1 and #2 may be removed from the scanned pattern sequence, scanned patterns #3 and #4 may be made the first and second values in the modified sequence with subsequent data values modified accordingly. As a result of such a process, the original data values #63 and #64 now become modified data values #61 and #62. As a result of the above steps an incomplete modified pattern of data values #1-#62 is generated. According to a preferred embodiment, modified data values #63 and #64 are generated by replicating data values #63 and #64 of the master patterns to which the modified scanned pattern is to be compared. If the modified patterns do not sufficiently match any of the master patterns, the modification process may be reiterated except that new scanned modified values #61-#64 are generated by replicating master pattern values #61-#64. This process is repeated until a sufficient match is found or until a predetermined number of modification iterations have occurred.
According to another preferred embodiment, scanned patterns may be modified backwards instead of the forward modification described above.
According to another preferred embodiment, master patterns may be modified instead of scanned patterns. According to this method, data values from scanned patterns are replicated into appropriate locations in modified master pattern sequences.
According to another preferred embodiment, trailing or leading sequence positions of modified master patterns may be filled with zeros instead of replicated data values from a scanned pattern to which modified master patterns are to be compared.
According to another preferred embodiment, modified master patterns with trailing or leading data values equal to zero are stored in a memory of an identification system along with corresponding unmodified master patterns, the master patterns and modified master patterns being stored before a bill under test is scanned by the identification system. When a bill under test is scanned by the identification system it is compared to one or more of the master patterns. If the identity of the bill can not be determined based on this comparison, the scanned pattern is compared with one or more of the modified master patterns. This process can be repeated, with the scanned pattern being compared to multiply modified master patterns if necessary.
According to another preferred embodiment, a currency evaluation device is provided that is able to discriminate among bills of different denominations from two or more currency systems. In a preferred embodiment, such a device is provided that is able to discriminate among both Canadian and German bills of different denominations. In a preferred embodiment, such a device utilizes three scanheads when scanning Canadian bills and a single scanhead when scanning German bills. The device is able to accept faced Canadian and German bills fed in either the forward or reverse directions. According to a preferred embodiment, the operator of the device pre-declares whether Canadian or German bills are to be discriminated. According to a preferred embodiment the measured length of the narrow dimension of German bills is utilized in discriminating German bills. To accommodate for possible lateral shifting of bills relative to the scanhead, multiple German master patterns associated with laterally displaced scans are stored for some denominations. To accommodate for possible lateral shifting of bills relative to the scanheads, multiple Canadian patterns associated with laterally displaced scans are generated and averaged in generated stored Canadian master patterns. To compensate for problems associated with triggering scanning relative to the edge of a bill, multiple patterns are stored for both Canadian and German bills associated with both leading and lagging printed indicia.